More than €2 billion has been wiped off the value of companies listed on the Irish stock market.
The heavy share losses were in line with similar performances in stock exchanges worldwide.
At close, the ISEQ index of shares was down by more than 4 per cent on the day to its lowest level this year, and at a lower point than in the immediate aftermath of last year's September 11th terrorist attacks on the United States.
The biggest faller was the Elan Pharmaceuticals group. The company's share collapsed by 52 per cent during the day, following a 66 per cent drop earlier this week.
Standard and Poor's cut Elan's credit rating by three notches to BB-minus from BBB-minus - deep into junk territory - citing Elan's shrinking access to capital and a possible funding need of more than $1 billion over the next two years.
The stock fell to a low of just €1.20 in morning trade, its second heavy fall in as many days, before edging back to €1.55 by close, down €1.98 on the day.
Plagued by accounting concerns ahead of the downgrade, Elan has lost over 90 per cent of its value so far this year.
The shares slump left the pharmaceutical giant worth a fraction of the almost €16.6 billion put on it at the start of the year.
The main financials were also down but not to the same extent. Allied Irish was 33 at €12.87 while Bank of Ireland was down 65 at €11.80.
Ryanair was down 43 cents to €5.65 while CRH was down 90 at €15.20.
